CA2020034A1

CA2020034A1 - Process for preparing polyurethane-backed carpet

Info

Publication number: CA2020034A1
Application number: CA002020034A
Authority: CA
Inventors: Kenneth W. Skaggs; Robert B. Turner; Terry L. Lamb
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1989-06-29
Filing date: 1990-06-28
Publication date: 1990-12-30
Also published as: EP0407084B1; ES2055330T3; EP0407084A2; DK0407084T3; AU627594B2; EP0407084A3; ATE107716T1; DE69010091D1; JPH0343243A; DE69010091T2; US4913958A; AU5796890A; JP2810770B2

Abstract

ABSTRACT

Substrates having successive layers of a cel-lular polyurethane and a non-cellular polyurethane are prepared using certain siloxane-polyether block copoly-mers in the non-cellular polyurethane formulation. The use of the block copolymer reduces or eliminates the formation of a bubble line at the interface of the poly-urethane layers, thereby improving physical and cosmetic properties of the carpet.

37,494-F

Description

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PROCESS FOR PREPARING
POLYURETHANE-BACKED SUBSTRATES, AND
THE SUBSTRATES SO PRODUCED
:.
This invention relates to the preparation of polyurethane-backed substrates, particularly textiles backed with a cellular polyurethane backing.

Polyurethane-backed textiles are well-known and described, for example, in U.S. Patent Nos.
10 3,821,130; 3,862,879; 3,296,159; 4,657,790; and 4,696,849. There are two general types of polyurethane backings commonly used. One type is a substantially non-cellular backing which is normally coated onto the back of tufted textiles to bind the individual tufts of 15 facing yarn to a primary scrim or grid. Such backings are often referred to as "unitary" backings. The other important type is a cellular backing which is attached to a textile to provide an attached cu~hion. In the carpet area, this type of backing often eliminate~ the 20 need to install a separate padding material.

` It is often desirable to apply multiple layers of the polyurethane. This is particularly true in pre-` 25 paring textiles with a cellular polyurethane backing.
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37,494-F - 1 -.
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In preparing these textiles, it is preferred to apply a substantially non-cellular polyurethane directly to the back of the textile, and then overcoat this "precoat"
with a cellular polyurethane layer. The precoat layer helps bind the facing material to the textile and pro-vides a smoother surface on which to apply the cellularlayer. This in turn helps to prepare a cellular layer of uniform gauge, which is of particular importance.

In order for the textile to have optimal prop-erties, it is necessary that the bonding between the textile and the various layers be as strong as possible.
- Unfortunately, quite often a line of bubbles develops at the interface between successive polyurethane layers, especially between the layers of non-cellular polyure-thane and cellular polyurethane. The bubble line weak-ens the bond between the layers to the point that they can often be easily peeled apart. When installed, forces applied to the exposed surface of the textile can cause a separation of the layers when such a bubble line is present. In addition, the presence of the bubble line is cosmetically unacceptable.

Accordingly, it is desirable to prepare a poly-urethane-backed textile wherein the bubble line between ; successive polyurethane layers is minimized or elimi-~ nated.
~ .
This invention is in one aspect a process for 3 preparing a polyurethane-backed substrate, wherein a ~ first layer of a polyurethane-forming composition is applied to a substrate and a second layer of a polyurethane-forming composition and is applied to said first layer said layers are cured, 37,494-F -2-202003~

wherein one of said first and second layers is a non-cellular polyurethane composition, and the other of said first and second layer is a cellular polyurethane composition, characterized in that said non-cellular polyurethane composition contains 0.03 to 2.0 weight percent of a polysiloxane-polyether block copolymer, said block copolymer containing 10 to 30 weight percent dialkylsiloxane units, 30 to 70 weight percent oxyethylene units and O to 55 weight percent other oxyalkylene units.
In another aspect, this invention is a sub-strate having attached thereto successive polyurethane :
layers, wherein one of such layers is a cellular poly-urethane which is attached directly to a non-cellular polyurethane layer characterized in that non-cellular polyurethane layer contains 0.03 to 2.0 weight percent of a polysiloxane-polyether block copolymer, said block copolymer containing 10 to 30 weight percent dialkylsiloxane units, 30 to 70 weight percent oxyethylene units and O to 55 weight percent other oxyethylene units.

; The incorporation of a block copolymer of the ; 25 type described into the non-cellular polyurethane-form-ing composition results in a very sub~tantial reduction, and often an elimination, of the bubble line between the polyurethane layers. This results in a stronger, more permanent bond between the layers.
. 30 ; In this invention, a substrate is attached directly or indirectly to two adjacent polyurethane layers. One of the polyurethane layers is non-cellular, 37,494-F -3-.

-which for the purposes of this invention means that the layer has a bulk density of at least about 0.8 g/cc.
The other polyurethane layer is cellular, which for the purposes of this invention means that the layer has a bulk density of less than 0.8 g/cc, preferably less than 0.6 g/cc, more preferably 0.05 to 0.6 g/cc, most preferably 0.2 to 0.6 g/cc. The two layers are advantageously formed by applying a polyurethane-forming - composition to a previously formed first polyurethane layer, and then curing said composition.
The non-cellular polyurethane layer is prepared from a polyurethane-forming composition containing a : certain polysiloxane polyether block copolymer. Certain of these materials are known as surfactants useful in preparing polyurethane foam. The polysiloxane portion is a dialkyl siloxane, preferably dimethyl siloxane, and constitutes 10 to 30, preferably 15 to 25 weight percent of the block copolymer. The poly(alkylene oxide) portion comprises oxyethylene units in an amount from 30 to 70, preferably 30 to 50, more preferably 30 to 45, ; weight percent of the block copolymer. In addition, the poly(alkylene oxide) portion may contain other alkylene ; oxide units, particularly oxypropylene units, in an amount from 0 to 55, preferably 30 to 559 more ` preferably 40 to 55, weight percent of the block Il copolymer.
These block copolymers often have terminal 3 hydroxyl groups. The terminal hydroxyl groups from the ~ poly(alkylene oxide) portion(s) of the block copolymer may, if desired, be capped with non-isocyanate reactive end groups so the block copolymer does not react with polyisocyanate groups in preparing the polyurethane 37,494-F -4-' ' ,~

layer. Generally, this is accomplished by reacting the terminal hydroxyl groups with a compound which will react with the hydroxyl group to form a non-isocyanate reactive end-group. Trialkyl silane, particularly tri-methyl silane, and ester, especially acetate, groups, are readily introduced and are preferred for that reason.

In addition, the block copolymer may contain the residues from polyhydric initiators.
. 10 The molecular weight of the block copolymer is not especially critical as long as it can be thoroughly blended with the other components of the polyurethane-; -forming composition, although those having a molecular 15 weight from 1000 to 100,000, preferably 3000 to 50,000, more preferably 10,000 to 50,000 are especially : suitable.
:
r 20 The block copolymer may be of the hydrolyzable (containing Si-0-C bonds) or nonhydrolyzable (containing Si-C bonds) type.
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Particularly suitable block copolymer~ are those having a dimethylsiloxane content of 15 to 25 weight percent, 30 to 45 weight percent oxyethylene units, 40 to 55 weight percent oxypropylene unit~, and a molecular weight from 10,000 to 50,000.

3 The block copolymer i~ used in an amount suf-~ ficient to reduce the formation of bubbles at the inter-face of the non-cellular and cellular polyurethane lay-ers. This is achieved when 0.03 to 2, preferably 0.1 to 37,494-F -5-202~34 0.5, weight percent of block copolymer are used, based on the weight of the polyurethane-forming composition.

In addition the block copolymer, the non-cellu-lar polyurethane composition advantageously contains at least one isocyanate-reactive material and at least one polyisocyanate. Suitable materials and compositions for preparing substantially non-cellular polyurethanes use-ful for backing a substrate are described, for example, in U.S. Patent Noss 4,296,159 and 4,696,849, both incorporated herein by reference.

The isocyanate-reactive material advantageously comprises a relatively high equivalent weight active hydrogen-containing material having an average function-ality from 1.7 to 3 and an average equivalent weightfrom 1000 to 5000. As used herein, the term "functionality" refers to the number of active hydrogen--containing groups (or in the case of polyisocyanate, the number of isocyanate groups) per molecule. The active hydrogen-containing groups are preferably hydroxyl groups, although carboxylic acid, thiol and primary or secondary amine groups may be present as well. A~ de~cribed in U.S. Patent No. 4,696,849, it is preferred to use materials having an average func-tionality of close to about 2Ø

Accordingly, it is preferred that the rela-tively high equivalent weight material have an average 3 actual functionality from 1.7 to 2.2, more preferably ~ from 1.8 to 2.1. Although a variety of materials such as polyester polyols, polyether polyol and polyacetals are useful, polyether polyols are by far the most preferred, due to low cost and particularly suitable 37,494-F -6-:, : ~ .
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properties. Most preferred are polymers of propylene oxide, especially those having terminal ethylene oxide capping, having an equivalent weight from 1000 to 2500 and a functionality from 1.8 to 2.1.
.
The non-cellular polyurethane composition also advantageously contains a polyisocyanate, such as described in U.S. Patents 4,296, 159 and 4,696,849.
Aromatic and aliphatic polyisocyanates are useful here-in, with the aromatic polyisocyanates being preferred and toluene diisocyanate (TDI), diphenylmethane diiso-cyanate (MDI), polymeric MDI and their respective deriv-atives and prepolymers being most preferred. Sufficient polyisocyanate is advantageously used to provide a ratio of isocyanate groups to active hydrogen-containing 5 groups of from 0.85 to 1.3, preferably from 0.95 to 1.2.
As discussed in U.S. Patent No. 4,696,849, the - polyisocyanate preferably is substantially difunctional, preferably having a functionality from 1.95 to 2.2.

In addition, it is often desirable to include in the polyurethane-forming composition a relatively low equivalent weight chain extender or cross-linker. Chain extenders are compounds having two active hydrogen-con-25 taining groups per molecule and an equivalent weight ~; from 31 to 1000, preferably from 53 to 200. Cross--linkerq are of similar equivalent weight but have in excess of two active hydrogen-containing groups per molecule. Of these, the chain extenders are preferred, 3 as their use permits the overall composition to have a - functionality of approximately 2Ø These materials are advantageously used in relatively small amounts compared to the amount of relatively high equivalent weight active hydrogen-containing material. Preferably, from 3 37,494-F -7-.
: `

-` 2020034 to 50, preferably from 3 to 30, more prePerably from 5 to 20 parts of the chain extender and/or cross-linker are used per 100 parts by weight relatively high equivalent weight active hydrogen-containing material.

In addition to the foregoing, various ancillary components may be used in the substantially non-cellular polyurethane-forming composition. Included among these are catalysts, blowing agents, fillers, antioxidants, colorants, antistatic agents, flame retardants and preservatives. Among these, catalysts and fillers are of particular interest.

Suitable catalysts include tertiary amine com-pounds and organometallic catalysts. Of the organome-tallic catalysts, organotin, organoiron and organobis-muth catalysts are of particular interest. The use of organoiron and organobismuth catalysts is described, for example, in U.S. Patent No. 4,611,044. Suitable organotin catalysts include dibutyltindilaurate, dimethyltindilaurate and stannous octoate. These catalysts are advantageously used in an amount from 0.001, preferably from 0.1 part by weight, up to 5 parts by weight for tertiary amine catalysts and up to about 0.5 part by weight for organometallic catalyqts.

It is usually desirable to employ an inorganic filler in order to reduce costs and to provide certain physical property enhancements. Suitable fillers 3 include aluminum trihydrate, calcium carbonate, carbon ~ black, titanium dioxide, kaolin and wollastonite.
Certain of these fillers provide flame retardancy (aluminum trihydrate) or coloration (carbon black and titanium dioxide), as well as function as fillers.

37,494-F -8-': ~

20200~
g Fillers, when used, are advantageously used in amounts from 30, preferably from 100, up to 300, preferably up to 225, more preferably up to 205 parts by weight per 100 parts relatively high active hydrogen-containing material.
Although blowing agents such as water, air, nitrogen and halogenated halocarbons may be used to produce the substantially non-cellular layer, their use is advantageously in an amount such that the density of the layer is at least about 0.8 g/cc. Most preferably, no blowing agent is used other than trace quantities of water which may be present as impurities.
.

The substantially non-cellular polyurethane 5 layer is advantageously formed by forming a layer of the corresponding polyurethane-forming composition onto the substrate or the cellular polyurethane layer and curing same. Methods for forming polyurethane layers on sub-20 strates are well-known and described, for example, in U.S. Patent Nos. 4,512,831; 4,595,436; 4,657,790 and 4,696,849. When the non-cellular polyurethane composition is applied to the substrate, it may or may not be cured before qubsequent application of the 25 cellular polyurethane-forming composition. However, it is preferred to at least partially cure the non-cellular layer before applying the cellular layer, and most preferred to cure it at least to a tack-free state.
Curing is readily effected by heating, such as in an 3 oven or using infrared lamps.

The cellular polyurethane layer is in direct contact with the non-cellular layer. The cellular layer is advantageously formed by applying a layer of a cellu-37,494-F _g_ ~" 2020034 --, o--lar polyurethane composition to the substrate or the non-cellular polyurethane layer and curing same. As stated before, in applying the two polyurethane layers, it is not necessary to cure the first-applied layer before applying the second layer, but such is preferred.

The cellular polyurethane-forming composition advantageously comprises a relatively high equivalent weight active hydrogen-containing material, a polyiso-cyanate and blowing agent. The high equivalent weight active hydrogen-containing materials and polyisocyanate are as described bePore with respect to the non-cellular polyurethane composition. The preferred polyisocyanates are TDI, MDI and polymeric MDI as well as prepolymers and derivatives thereof. The most preferred relatively high equivalent weight active hydrogen-containing mate-rials are polymers of propylene oxide, especially those end-capped with oxyethylene units, having an equivalent weight of from 1000 to 2500. The preferred func-; 20 tionality is from 2 to 3 when TDI or prepolymers or derivatives thereof are used as the polyisocyanate, and from 1.7 to 2.2 when MDI or prepolymers or derivatives thereof are used. The amount of polyisocyanate used is as described before.
The blowing agent i~ advantageously water, ahalogenated hydrocarbon, air, nitrogen, or other mate-rial which generates a gas under the conditions of the reaction of the cellular polyurethane composition. It is preferred to froth the composition using suitable ~ equipment, in order to whip air or other inert gas into the composition. Such processes are described in U.S.
Patents 3,821,130 and 3,862,879. In such processes~
some water may be included for additional density 37,494-F -10-', 202003'1 1, reduction. Sufficient blowing agent is used to obtain the densities described before.

In addition to the foregoing components, aux-iliary components such as fillers, catalysts and cross--linkers as described before with respect to the non--cellular polyurethane-forming composition, may be used.
It is particularly preferred to employ an organometallic catalyst and from 50 to 150 parts of an inorganic filler per 100 parts of relatively high equivalent weight active hydrogen-containing material. In addition, addition of ~ small amount of a silicone block copolymer is preferred to stabilize the cells of the reaction mixture until it has cured sufficiently to maintain its cellular configuration.

The choice of substrate is not especially cri-tical, and metals, leathers, plastic films, wood sur-faces, papers, cardboards and a wide variety of other materials are suitable as the substrate. Of particular interest, however, are woven and non-woven textiles.
Among these, of particular interest are textiles suit-able for preparing floor coverings, including jute or other webbings, scrims, woven carpets and e~pecially non-woven carpets. The weight of the substantially non--cellular polyurethane layer is advantageously from 8 to 40, preferably from 12 to 35, ounces/ square yard. The weight of the cellular polyurethane layer is advantageously from 10 to 40, preferably from 15 to 35, 3 ounces/square yard.

Formation of the polyurethane-forming composi-tions into layers and applying same to a substrate is well-known. For example, the processes described in 37,494-F -11-202003~

U.S. Patent Noss 4,512,831; 4,515,646; and 4,657,790 are suitable for this purpose. In general, these processes involve forming a mixture of all components except the polyisocyanate and sometimes the catalyst, then blending in the polyisocyanate (and catalyst if needed) and imme-diately applying same to the substrate A doctor bar orrollers are suitable for marrying the polyurethane com-positions to the substrate. Curing is advantageously effected by heating, such as in an oven, by infrared heating lamps, or other suitable means.
.. 10 In preparing floor covering according to this invention, it is most preferred to apply the non-cellu-lar polyurethane layer to the back of the textile, and then to overcoat this layer with a layer of a cellular polyurethane. This is particularly true when the tex-tile is a tufted textile, as the first non-cellular layer serves to glue the tufted fibers to the primary backing material.

The following examples are given to illustrate the invention and are not intended to limit the scope thereof. Unless stated otherwise, all parts and per-centages are given by weight.

Example 1 and Comparative Samples A-D
A non-cellular polyurethane composition was - 30 prepared from the materials li~ted in Table 1.

37~494-F -l2-, :, : '''''-- ~

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Parts by Component Wei~ht Polyol A~ 85 Dipropylene glycol 15 Calcium carbonate 105 Aluminum trihydrate 100 Organotin catalyst 0.1 Silicone surfactant~ variable TDI prepolymer~ 110 index A 1000 equivalent weight poly(propylene oxide) having a nominal functionality of 2Ø
~ Type and amount indicated in Table 3.
: ~ A soft segment prepolymer having an equivalent weight of about 156.7 and an average functionality of~2.06.

Carpet Sample Nos. 1-7 and Comparative Samples A, B and C were prepared in the following general proce-dure. All the materials except the prepolymer and cata-lysts were thoroughly mixed at room temperature. The prepolymer was then mixed in with the other components, followed by the catalyst. The re-qulting mixture was then poured onto a tufted Camalon yarn level loop carpet and ~craped down to form a layer having a coating weight of about 32 ounces/qquare yard. In preparing Sample - 3 Nos. 1-4 and Comparative Samples A and B, this coated sample was then placed on top of a 60C aluminum plate, and a 1/8" layer of a cellular polyurethane composition was applied. The cellular polyurethane composition was as described in Table 2. The resulting composite and 37,494-F -13-. '' :' ~ .

- 2020~34 underlying aluminum plate were transferred to a 120C
oven and cured. In preparing Sample Nos. 5-7 and Comparative Sample C, the non-cellular polyurethane was cured before applying the foam-forming composition.

Parts by ; Component Wei~ht Polyol B~ 90 10 Diethylene glycol 10 Aluminum trihydrate 50 Calcium carbonate 60 Block copolymer~ variable 15 Organotin catalyst 0.08 TDI prepolymer~ 110 index A 1666 equivalent weight poly(propylene oxide) having a nominal functionality of 3.0 and 15 wt percent ethylene oxide capping.
~ Type and amount indicated in Table 3.
~ See note ~ of Table 1.

: 25 The type and amount o~ block copolymer in the respective polyurethane layers, and the results of these evaluations are reported in Table 3.

37,494-F -14-, -~ 2020a3~

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o o 0 E~ ¢ m ¢ ~ ¢ ¢ ¢ ¢ m ¢ ,d O ~J 3 0 ~
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37 r 494-F -15-.' 202003~

As can be seen from the data in Table 3, addi-tion of a block copolymer to the non-cellular layer caused a substantial decrease in the amount and size of the bubbles at the interface of the two polyurethane layers. The inclusion of a block copolymer in the cel-lular layer had little effect on the bubble line. The effect of the bubble line on the physical integrity of the carpet was determined subjectively by attempting to pull the cellular polyurethane layer from the composite.
In those samples with a large bubble line, the cellular layer delaminated easily at the interface with the non--cellular layer. As the size and number of the bubbles decreased, delamination became more difficult. In Sample Nos. 3-7 delamination was quite difficult, with the mode of failure often being tearing of the cellular polyurethane layer itself.

Comparative Sample D was prepared by repeating Comparative Sample C, substituting a Wellco Columbia tufted carpet for that used in Comparative Sample C. A
bubble line containing many large bubbles was present.
When this sample was again repeated with the Wellco Columbia carpet and 0.125 parts Block copolymer B in the non-cellular composition (Example 8) the bubble line was e~sentially eliminated.

When this experiment was repeated (Example 9) using no block copolymer in the cellular polyurethane composition and 0.5 part of a 6700 molecular weight block copolymer containing about 21 percent ~ dimethylsiloxane units, 32 percent oxyethylene units and 47 percent oxypropylene units in the non-cellular polyurethane composition, the bubble line was eliminated.

37,494-F -16-.
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Claims

1. A process for preparing a polyurethane--backed substrate, wherein a first layer of a polyurethane-forming composition is applied to a substrate and a second layer of a polyurethane-forming composition is applied to said first layer and said layers are cured, wherein one of said first and second layers is a non-cellular polyurethane composition, and the other of said first and second layers is a cellular polyurethane composition, characterized in that said non-cellular polyurethane composition contains from 0.03 to 2.0 weight percent of a polysiloxane--polyether block copolymer, said block copolymer containing from 10 to 30 weight percent dialkylsiloxane units, from 30 to 70 weight percent oxyethylene units and from 0 to 55 weight percent other oxyalkylene units.

2. The process of Claim 1 wherein said poly-siloxane-polyether block copolymer contains dimethyl-siloxane and oxypropylene groups and has a dimethylsil-37,494-F -17-oxane content of from 15 to 25 percent, an oxyethylene content of from 30 to 50 percent, and an oxypropylene content of from 30 to 55 percent.

3. The process of Claim 2 wherein said non--cellular polyurethane composition comprises (a) a polymer or copolymer of propylene oxide having an equivalent weight from 1000 to 2500, an average functionality for 1.8 to 2.2, (b) TDI, MDI or a prepolymer or derivative thereof, and (c) from 30 to 225 parts by weight of an inorganic filler, per 100 parts by weight polyether polyol.

4. The process of Claim 3 wherein said cel-lular polyurethane composition comprises (a) polymer or copolymer of propylene oxide having an average function-ality from 1.8 to 2.1 and an average equivalent weight from 1000 to 2500, (b) TDI, MDI or a prepolymer or derivative thereof and a sufficient quantity of a blowing agent to provide the cellular polyurethane with a density from 0.2 to 0.6 pound/cubic foot.

5. The process of Claim 2 wherein said non--cellular polyurethane composition contains a relatively high equivalent weight active hydrogen-containing mate-rial and from 0.1 to 0.5 part of said block copolymer per 100 parts by weight relatively high equivalent weight active hydrogen-containing material.

6. The process of Claim 4 wherein said non--cellular polyurethane composition contains from 0.1 to 0.5 part of said block copolymer per 100 parts by weight of said polyether polyol 37,494-F -18--l9-

7. The process of any one of the preceding claims wherein said substrate is a textile.

8. A substrate having attached thereto suc-cessive polyurethane layers, wherein one of such layers is a cellular polyurethane which is attached directly to a non-cellular polyurethane layer characterized in that the non-cellular polyurethane layer contains from 0.03 to 2.0 weight percent of a polysiloxane-polyether block copolymer, said block copolymer, said block copolymer containing from 10 to 30 weight percent dialkylsiloxane units, from 30 to 70 weight percent oxyethylene units and from 0 to 55 weight percent other oxyalkylene units.

9. The substrate of Claim 8 wherein said dialkylsiloxane units are dimethylsiloxane units, said other oxyalkylene units are oxypropylene units, said block copolymer contains from 15 to 25 weight percent dimethylsiloxane units, from 30 to 45 weight percent oxyethylene units and from 40 to 55 weight percent oxypropylene units, and said block copolymer has a molecular weight from 10,000 to 50,000.

37,494-F -19-